Conventionally, there is known a connection terminal structure in which a connection terminal having a spring-like property is bonded to a pad of a substrate (see, for example, Japanese Laid-Open Patent Publication No. 2011-014451). In the connection terminal structure, an upper surface of the pad (hereinafter also referred to as “pad upper surface”) of the substrate is bonded, by way of solder, to a surface of the connection terminal that faces the pad upper surface (pad facing surface).
However, the solder not only adheres to an area between the pad upper surface of the substrate and the pad facing surface of the connection terminal but also adheres to a surface of a part of the connection terminal (extending surface) that extends from the pad facing surface. That is, residual solder that is wetted and spreads from the area between the pad upper surface and the pad facing surface may adhere to the extending surface of the connection terminal. The amount and shape of the residual solder adhered to the extending surface of the connection terminal are not uniform and may vary with respect to each connection terminal.
The varying of the amount and shape of the residual shape may lead to inconsistencies among the connection terminals. For example, the spring constant of each connection terminal or the height between a surface of the substrate and a tip of the connection terminal may vary. This may lead to degradation of connection reliability between the connection terminal and a connection target.